The present invention relates to a filter device for filtering liquids having a filter element arranged in a filter housing with the liquid to be filtered flowing through the filter element.
Published German Patent Application No. DE 197 46 752 A1 describes an oil and/or fuel filter having a cylindrical filter insert in a filter housing where the medium to be filtered flows radially through the filter from the outside to the inside. After filtering, the filtered medium is discharged axially from the interior of the filter insert. To ensure that the unfiltered liquid side and the filtered liquid side of the filter insert are separated with a fluid-tight and pressure-tight seal, the axial end faces of the filter insert are sealed with end disks to prevent leakage flows, and a sealing ring is inserted into the central recess in the end face of the filter insert, thereby forming a seal between the filter insert and the adjacent housing.
The filter device disclosed in published German Patent Application No. DE 197 46 752 A1 is particularly suitable for feeding the medium to be filtered radially into the filter housing because the sealing rings inserted into the end face make axial feed of the medium impossible, since the medium would enter directly into the filtered liquid chamber of the filter element.
On the other hand, an axial feed of medium may offer advantages for structural reasons and because such a filter device can be integrated into a pipeline especially easily. In this case, however, the axial end face of the filter element must be sealed liquid-tight with a cover, whereupon the medium that is to be filtered and is introduced into the filter housing flows past the cover of the filter element on the end face and enters an annular space running radially around the filter element, flowing from there radially from the outside to the inside through the filter material.
Problems may occur, however, when the medium to be cleaned has a relatively high freezing point. At cold ambient temperatures, the liquid medium introduced axially into the filter housing may freeze, whereupon the cover may be destroyed due to the expansion of the medium when it freezes, thus also destroying the entire filter element.